An erect equal-magnification lens array is formed by superimposing plural flat lens plates, on both sides of which a large number of convex lenses are arrayed, one on top of another. Specifically, the erect equal-magnification lens array is formed by superimposing plural resin lens plates, in which a large number of convex lenses are arrayed on both sides of a transparent substrate, one on top of another.
As technique concerning the erect equal-magnification lens array, JP-A-2004-70268 is known. According to the technique proposed in JP-A-2004-70268, in an erect equal-magnification lens array formed by superimposing plural lens plates, on both sides of which convex lenses are arrayed and formed, one on top of another, a lens pitch P in an arraying direction of the convex lenses is twice or more as large as the height of a reversed image formed in the erect equal-magnification lens array. Aperture stops are provided in respective lens elements in order to prevent beams from passing through a position where the reversed image is formed except circles having the height of the reversed image as a radius. This makes it possible to reduce occurrence of stray light and flare light.
However, the technique proposed in JP-A-2004-70268 cannot completely prevent the occurrence of stray light and flare light although the technique can reduce the occurrence of stray light and flare light. Stray light that should not originally be made incident on adjacent lens arrays is made incident on the adjacent lens arrays to deteriorate an MTF (Modulation Transfer Function). To reduce the stray light itself, it is necessary to insert aperture stops having required thickness on an incident surface side of the lenses. However, since a part of light made obliquely incident on the incident surface side of the lenses is blocked, an amount of light made incident on the lens array is reduced.